The demand for electronic devices and optoelectronic devices for the infrared range can be met by semiconductor heterostructures based on group-III antimonides. From III-V compound semiconductor materials, antimonides offer a comparable small band gap, from 1.65 eV of AlAsSb down to 0.2 eV of InSb. Therefore, devices based on III-V-antimonide-heterostructures are well-suited as emitters for optical data transmission, solar energy harvesting, gas sensing applications, medical applications, plastic welding, etc.
For the fabrication of high-quality electronic and optoelectronic semiconductor devices, a precise control of the electronic band structure is desired. Accordingly, heterostructures with tailored compositional transitions are desired. In particular, layer quality after growth and the potential impact of high temperature processing steps on the layer quality have to be controlled and known. One aspect to be considered is interdiffusion resulting in a degradation of steep concentration profiles.
For example, semiconductor lasers operating in the 2-5 micrometer range and providing a high output power are a common desire. Such a semiconductor laser can be constructed of a stack of layers, typically III-V-semiconductors, formed on a binary substrate, such as GaSb, GaAs, InP, Si, InSb, InAs, GaP, or Ge. Some applications have employed semiconductor lasers with binary or/and ternary compounds for the waveguide and active region, while other applications use quaternary compounds or even quinternary compounds. For example mixed group-V quaternary alloys can be GaInAsSb, AlGaAsSb, and AlInAsSb, whereas AlGaInAsSb can be a quinternary alloy.
Particularly for high performance electronic and optoelectronic devices with band structures, which are complex and/or difficult to grow, as well as doping levels, which are complex and/or difficult to manufacture, interdiffusion or intermixing of materials in binary, ternary, quaternary and quinternary systems need to be considered and controlled.
Typically, heterostructures in binary, ternary, quaternary and quinternary system are grown under group-V-rich conditions, because group-III-rich conditions have been experiences to be disadvantageous due to droplet formation and the like. Further, there have been attempts to generate group-III-rich surfaces from group-V-rich surfaces, e.g. by heating in order to achieve a group-III-rich surface reconstruction of a semiconductor layer. This is for example described in patent application publication US 2009/0085073.
In view of the above, it is an object of the present invention to provide an improved semiconductor structure and improved methods of manufacturing thereof that overcome at least some of the problems in the art.